The present invention is directed to processes for preparing mixed solvent adhesives useful in bonding belts used in electrostatographic, including digital printing apparatuses. In specific embodiments, the present invention is directed to processes for preparing mixed solvent adhesives useful in seaming belts, and more specifically, to endless flexible seamed belts wherein an image can be transferred at the seam of the belt with little or no print defects caused by the seam. In embodiments, the present invention relates to processes for preparing adhesives useful in xerographic component imageable seamed belts comprising mutually mating elements of a seam, wherein the adhesive is present between mutually mating members. The process for preparing mixed solvent adhesives comprises mixing alcohol and acetates to the adhesive components. More specifically, the process comprises mixing an alcohol and a polymer to form an adhesive solution; mixing a charge transporting molecule and a solvent other than alcohol (such as, for example, an acetate) so as to form a charge transport solution; adding the charge transport solution to the adhesive solution to form a mixed solvent solution; mixing an electrically conductive filler and a solvent to form a filled solvent solution; and mixing the filled solvent solution with the mixed solvent solution so as to form a mixed solvent adhesive solution. In optional embodiments, a crosslinking agent can be added in order to crosslink the adhesive in solution upon curing. In optional embodiments, a nonionic surfactant can be added to enable coatability of the adhesive.
In a typical electrostatographic reproducing apparatus such as an electrophotographic imaging system using a photosensitive member, a light image of an original to be copied is recorded in the form of an electrostatic latent image upon a photosensitive member and the latent image is subsequently rendered visible by the application of a developer mixture. One type of developer used in such printing machines is a liquid developer comprising a liquid carrier having toner particles dispersed therein. Generally, the toner is made up of resin and a suitable colorant such as a dye or pigment. Conventional charge director compounds may also be present. The liquid developer material is brought into contact with the electrostatic latent image and the colored toner particles are deposited thereon in image configuration.
In a more typical electrostatic reproducing apparatus, the developer consists of polymeric coated magnetic carrier beads and thermoplastic toner particles of opposite triboelectric polarity with respect to the carrier beads. This is the dry xerographic process.
The developed toner image recorded on the imaging member is transferred to an image receiving substrate such as paper via a transfer member. The toner particles may be transferred by heat and/or pressure to a transfer member, or more commonly, the toner image particles may be electrostatically transferred to the transfer member by means of an electrical potential between the imaging member and the transfer member. After the toner has been transferred to the transfer member, it is then transferred to the image receiving substrate, for example by contacting the substrate with the toner image on the transfer member electrostatically or under heat and/or pressure.
Transfer members enable high throughput at modest process speeds. In four-color photocopier or printer systems, the transfer member also improves registration of the final color toner image. In such systems, the four component colors of cyan, yellow, magenta and black may be synchronously developed onto one or more imaging members and transferred in registration onto a transfer member at a transfer station.
In electrostatographic printing and photocopy machines in which the toner image is transferred from the transfer member to the image receiving substrate, it is desired that the transfer of the toner particles from the transfer member to the image receiving substrate be substantially 100 percent. Less than complete transfer to the image receiving substrate results in image degradation and low resolution. Complete transfer is particularly desirable when the imaging process involves generating full color images since undesirable color deterioration in the final colors can occur when the color images are not completely transferred from the transfer member.
Thus, it is desirable that the transfer member surface has excellent release characteristics with respect to the toner particles. Conventional materials known in the art for use as transfer members often possess the strength, conformability and electrical conductivity necessary for use as transfer members, but can suffer from poor toner release characteristics, especially with respect to higher gloss image receiving substrates.
Polyimide substrate transfer imaging members are suitable for high performance applications because of their outstanding mechanical strength and thermal stability, in addition to their good resistance to a wide range of chemicals. However, the high cost of manufacturing unseamed polyimide belts has led to the introduction of a seamed belt. Even polyimides with the best mechanical and chemical properties often exhibit poor adhesion at the seam even when commercially available primers and adhesives are used.
In the electrostatic transfer applications, use of a seamed transfer polyimide member results in insufficient transfer in that the developed image occurring on the seam is not adequately transferred. This incomplete transfer is partially the result of the difference in seam height to the rest of the belt. A xe2x80x9cbumpxe2x80x9d is formed at the seam, thereby hindering transfer and mechanical performance. The development of puzzle cut seams has increased the quality of transfer somewhat, by decreasing the seam height, thereby allowing smooth cycling. However, even with the improvements made with puzzle cut seams, quality imaging in the seamed area has not been obtainable at present due, in part, to contrast in transfer caused by differences in electrical and release properties of known seaming adhesives. Further, current adhesives do not provide sufficient bonding strength at the seam, resulting in short belt life. In addition, the seam must have the appropriate surface properties in order to allow for sufficient toner release at the seam.
Currently, puzzle cut and overlap seam adhesives consist of uv-curable epoxies and hot-melt adhesives. While these adhesives exhibit acceptable strengths at room temperature under tensile load, most undergo premature failure at elevated temperatures. Additionally, the existing adhesives have been found to perform poorly under some important dynamic test conditions. Because the adhesive seam is not imageable, most machines do not develop images on the seam area, or non-seamed belts are used.
Improved seam adhesives such as polyamic acid adhesives have proven to be strong. However, adhesives such as polyamic acid adhesives require long cure times at elevated temperatures (for example, 1 hour at 200xc2x0 C.) with loss of water as the polyimide seam is formed. The resulting differential shrinkage causes ripples as the adhesive cures and the cured seams are not completely filled with adhesive. If one side of the puzzle cut seam is glued, tenting occurs. If both sides of the puzzle cut seam are treated with polyamic acid adhesive, ripples form. Such ripples in the seam cause uneven development and ultimately result in print defects, and a reduced belt life. Thus, adhesive alternatives to polyamic acid must be considered.
Polyamide adhesives have solved many of the above problems. However, many polyamide adhesives are alcohol soluble. This creates a significant problem from a coating standpoint, because it is difficult to generate uniform coatings of polyamide alcohol formulations using commercial equipment, even when a number of different release liners are used. In addition, the thickness of the known adhesives must be built up with successive coatings, instead of having the ability to be coated with one pass.
Therefore, it is desirable to provide an adhesive system that solves many of the above problems, but with the ability to provide uniform adhesive coatings to be used with a number of different release liners and that can be coated to a desired thickness in one pass.
U.S. Pat. No. 5,549,193 relates to an endless flexible seamed belt comprising puzzle cut members, wherein at least one receptacle has a substantial depth in a portion of the belt material at the belt ends.
U.S. Pat. No. 5,721,032 discloses a puzzle cut seamed belt having a strength-enhancing strip.
U.S. Pat. No. 5,487,707 discloses a puzzle cut seamed belt having a bond between adjacent surfaces, wherein an ultraviolet cured adhesive is used to bond the adjacent surfaces.
U.S. Pat. No. 5,514,436 relates to a puzzle cut seamed belt having a mechanically invisible seam, which is substantially equivalent in performance to a seamless belt.
Embodiments of the present invention include: a process for preparing a mixed solvent adhesive solution comprising a) mixing an alcohol and a polymer to form an adhesive solution; b) mixing a charge transporting molecule and an acetate to form a charge transport solution; c) adding the charge transport solution of (b) to the adhesive solution of (a) to form a mixed solvent solution; d) mixing an electrically conductive filler and a solvent to form a filled solvent solution; and e) mixing the filled solvent solution of (d) to the mixed solvent solution of (c) so as to form a mixed solvent adhesive solution.
In addition, embodiments of the present invention include: a process for preparing a mixed solvent adhesive solution comprising: a) mixing an alcohol and a polymer to form an adhesive solution; b) mixing a charge transporting molecule and a solvent other than an alcohol, so as to form a charge transport solution; c) adding the charge transport solution of (b) to the adhesive solution of (a) to form a mixed solvent solution; d) mixing an electrically conductive filler and a solvent to form a filled solvent solution; and e) mixing the filled solvent solution of (d) to the mixed solvent solution of (c) so as to form a mixed solvent adhesive solution.
Embodiments further include: a process for preparing a mixed solvent adhesive solution comprising a) mixing an alcohol and a polyamide adhesive to form an adhesive solution; b) mixing a charge transporting molecule and an acetate so as to form a charge transport solution; c) adding the charge transport solution of (b) to the adhesive solution of (a) to form a mixed solvent solution; d) mixing an electrically conductive filler and a solvent to form a filled solvent solution; and e) mixing the filled solvent solution of (d) to the mixed solvent solution of (c) so as to form a mixed solvent adhesive solution.